These are not 1/2" cutting diameter. The 1/2" means you can thread mill an internal thread as small as 1/2"-13. Please note;

Specs: 3/8" shank, 0.372" cutting diameter, 4 Flutes, 0.240" neck diameter, 1-1/4" reach depth, 3" overall length. Use for milling 1/2" diameter threads or larger. Internal or external threads from 12-48 TPI.